Disclosed herein is an apparatus and method that detaches media from a fuser in a printer.
Presently, fusers are used in image generation devices, such as printers, to fuse a latent image on media, such as a document, by applying pressure and heat to the image on the document. When the fused document exits the fuser, the document may stick to the fuser roll. Some devices use stripper fingers to strip the document from the fuser roll. Unfortunately, the stripper fingers can cause a mottle look on the document where the fingers contact the document when stripping it from the fuser roll.
Other devices use air knives to strip the document from the fuser roll. An air knife or a plurality of air knives strip a document from a fuser roll by blowing pressurized gas between the document and the fuser roll to strip the document at or close to a fuser roll nip. This can result in a smooth looking fused image on the document. This can also result in the document bouncing around in the air knife baffle, creating slag with the document waving or flopping around in the air knife baffle chamber.
After initially stripping the lead edge of the document off the fuser roll, the air knife system shuts off and the document self strips off the fuser roll in the air knife baffle. At this point, the striping function relies on the document stiffness to continue the self stripping. This change in stripping function changes the strip point location of the document relative to the fuser roll because part of the document re-tacks to the fuser roll. Different document strip points create image quality defects showing a visible transition in solids resulting from the air turning off. Furthermore, the document sheet may take a curved trajectory after being stripped before the lead edge is in a decurler exit nip causing the document sheet to buckle. If there is a buckle after the air knife is turned off, the sheet strip point moves away from the fuser nip, further causing image quality defects.
As mentioned, the image quality defects are evidenced by a difference between a smooth image appearance and a mottle image appearance on the document. For example, if the document is stripped closer to the fuser nip, the resulting image is smoother. If the document is stripped at a location after the nip, the resulting image has a mottle look. In documents that use coated media, the transition from smooth to mottle is especially noticeable to customers, which is evidenced by maintenance requests precipitated by image quality defect.
One approach to eliminate or limit the image quality defect is to leave the air knife on while the whole document sheet passes through the fuser. This requires a higher air knife pressure capacity, which requires a bigger compressor. Unfortunately, a bigger compressor is more costly, requires more power, requires major hardware changes, and results in higher noise levels. Furthermore, excessive use of air knives excessively cools the fuser roll. Also, excessive use of air knives cause streaks created by the air jets on some coated documents. Additionally, air knives can cause air streaks due to an interaction of air temperature and document corrugation. For example, multiple air knives blow air under the document at certain points creating ridges, but the document still sticks a bit to fuser at other points creating grooves, thus wrinkling the document.
Thus, there is a need for an improved apparatus and method that detaches media from a fuser in a printer.